Category: ChitChat

Today my kids impressed me by repurposing/hacking/misusing the toilet-occupied-light to send (morse-like) signals across a railway car. Their fingers were thin enough to press the micro-switches in the doors which normally would signal a locked door (i.e. occupied toilet). Not sure if someone noticed the strangely flashing lights… 😀

Last weekend I had to replace a 230 V fan (120 mm), a Sunon DP200A, that ‘smelled’ strange and also made strange noises. Better safe than sorry…

Well: I ordered a slightly less powerful Sunon DP201A (at Reichelt Elektronik) to replace the possibly dangerous fan. Although they look similar their connectors are completely different. So I’m now wondering if the first one (the DP200A) wasn’t an original fan at all…?

Half a year ago I’ve started to use KiCad for new PCB designs I’m working on. I already wanted to try out KiCad for quite some time. Its release 4.0 and the latest changes in EagleCAD (annoying ads and recently being bought by Autodesk) were enough pressure to switch. And what should I say: after dealing with the rather unhandy library management and some cryptic error messages I really now enjoy KiCads workflow.

Based on a recent Twitter conversation I had a thought about bank and credit card PIN numbers (sorry for the redundancy): are really all possible PINs issued or are some kept back because bank customers could feel uncomfortable with certain combinations of digits? And would it really matter if some of them were kept back?

It should be obvious that in case of a truly random PIN 4 identical digits are just as likely to occur as any other combination. But certain combinations just do not feel random (I don’t know how to explain it better, I’m not a psychologist).
So I’ve made a small Gedankenexperiment:

Let’s assume that a bank issues by default a 4-digit PIN. (I know that my bank issues 4-digit PINs by default but they can be changed to any 4- to 6-digit number afterwards.)

Customers would not accept a PIN with four identical digits (0000, 1111, …, 9999) out of fear that they might be insecure.

An ATM allows 3 attempts to enter a PIN before locking/withholding a bank/credit card. (This limit is actually the main reason why 4-digit PINs are mostly safe, btw.)

From time to time I have (and take) the chance to dumpster dive for electronic parts. Recently, on one of these occasions, an old piece of hardware felt into my hands: a “Moser Galvanosan” galvanic stimulator.

To be honest, I’ve had no idea what it was and at first I only thought it would be a nice case for another project I was working on. After some research (out of curiosity) I thought the device is interesting enough to take some photos of its interior and write about it.

Disclaimer: I’m totally not into alternative medicine or stimulation current therapy. I’m just taking an interesting looking piece of hardware apart, that’s all!

Well, today is the first Sunday of Advent… time to play around with my cutting machine. 😉

I got inspired by a post on Hackaday.com (on Laser-cut Gift Boxes). The post presents a really nice source for DXF files for various shapes for card stock boxes. Out of curiosity I simply ‘threw’ some of their design files at my electronic cutting machine. They might save me some time (gift wrap, you know). The result is a short video of the process, nothing special:

While trying to explain the meaning of the carry digit during addition an subtraction to my oldest son, I’ve given him a nice little device to play with: the Addifix-9 number cruncher.

I’ve briefly mentioned this device before in a post. This time I’ve made a short video about the mechanical calculator in action and present more details:

In the 1950s/60s The Addifix series was sold as “Addifix-9 Taschenrechenmaschine” by the German mail-order company Neckermann. Its predecessor was the Addiator from Carl Kübler which was sold since the early 1920s [Source: sliderulemuseum.com]. The underlying mechanical principle is quite old (an documented example is the mechanical calculator by Claude Perrault from the 17th century).

The Addifix is a pocket-sized (13 x 9 cm) slide adder that can be used from both sides – one side for addition and one for subtraction. The slides (one for each digit) are handled with a metal stylus.